vmstat显示的buffer和cache的区别

最新推荐文章于 2025-05-07 09:45:00 发布

原创最新推荐文章于 2025-05-07 09:45:00 发布 · 975 阅读

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#Cache #Linux #ASP #performance #Blog

本文通过使用vmstat命令展示了如何查看Linux系统的内存使用情况，并详细解释了buffers与cache的区别及其作用。buffers主要用于文件元数据和原始块设备数据的缓存，而cache则用于文件数据块和通过mmap调用映射到内存的文件信息。

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Try the manual first.

  $ man vmstat
   ...
   Memory
       swpd: the amount of virtual memory used (kB).
       free: the amount of idle memory (kB).
       buff: the amount of memory used as buffers (kB).
       [红帽子8.0的Man中没有这一行]
       cache: the amount of memory used as cache.
    ...

See what's on my Red Hat Linux server.

$ vmstat

   procs                      memory    swap          io     system         cpu
r b w   swpd   free   buff cache si so    bi    bo   in    cs us sy id
0 0 0      0 316488 159612 493916   0   0     0     6   22    23 13   2 14

Answers Googled:

To answer your question, buffers are only used for file metadata (inodes, etc) and data from raw block devices. It's accessed via block device and block number.
Cache has file data blocks, and memory mapped information (i.e. files mapped with mmap() calls). It's accessed primarily via inode number.
So, the main difference would be scope, I guess. One's more concerened with blocks on a device, the other with information in a file.

Either buffer can flush to disk, however. The buffer to the device file and the cache through the file system layer to the block device.

参考资料：

1. Red Hat Manuals

2. Linux Memory Management

3. System Performance Tuning, 2nd Edition, read Chapter 4 Memory online.

or buy Chinese edition from china-pub.

http://blog.china-pub.com/more.asp?name=uniware&id=5345